Introduction: The Modified Circle System was developed to reduce the amount of oxygen required
for long-distance transportation of ventilated patients. Formal testing of the system
has never been documented. Various aspects of the system were tested, with the study
broken into four parts.
Methods: Bench testing was performed with a test lung that simulated two different lung compliances.
Four ventilators were tested with the system. The four parts to the study were oxygen
flow rates, position of oxygen inflow, pressure drop across the system, and specific
testing with the LP 10 ventilator.
Results: The minimum oxygen flows required to maintain forced inspiratory oxygen (FiO2) higher than 0.93 over a range of ventilator and lung settings was 1.5 L/min. The
oxygen inflow is best connected directly to the CO2 absorber unit. A significant pressure drop occurs across the system, which increases
progressively with higher ventilator pressures. The LP 10 does not allow improved
oxygen conservation when recycling gases via its air inlet port.
Conclusion: The study provides previously unknown, clinically important information regarding
the performance of the Modified Circle System.
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Reference
- Oxygen conservation during long distance transport of ventilated patients.Air Med J. 2005; 24: 164-171
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© 2006 Air Medical Journal Associates. Published by Elsevier Inc. All rights reserved.
